Fluid jet looms conventionally include a source of pressurized fluid, a main or primary weft insertion nozzle and a plurality of auxiliary weft insertion nozzles, as well as a plurality of individual flexible pressure hoses that connect the pressure source to the several nozzles. Electrically actuatable magnetic valves are also typically interposed between the pressure source and the nozzles, in order to control the supply of pressurized fluid from the source to the nozzles, according to a program being executed by the general loom controller. In this regard, the main weft insertion nozzle inserts a weft thread into an open loom shed as pressurized fluid is supplied to this nozzle, and then the auxiliary nozzles carry the inserted weft thread across the width of the open shed, for example along a weft insertion channel provided in the reed of the loom. In a typical air jet loom, the pressure source is a source of pressurized air, and the nozzles are corresponding air jet nozzles. Alternatively, a liquid, such as water may be provided from the pressure source to drive appropriate water jet nozzles.
In the operation of such fluid jet looms, the flexible pressure hoses are subjected to a great variety of loads and stresses during the weaving process. Such loads and stresses include bending loads and stresses at the terminal hose connections, as well as pressure loads and stresses of the entire hose and its connections as a result of the repetitive increasing and decreasing of the pressure within the hose during the course of the weaving operation. Since the magnetic valves controlling the flow of the pressurized fluid cycle open and closed during the weaving operation, there is a corresponding drastic and rapid variation of pressure in the associated pressure hoses. Also, the vibration and motion of various mechanical components of the loom cause corresponding vibration and motion of the pressure hoses and the hose connections provided at the ends of the hoses.
These various loads and stresses cause long term fatigue of the pressure hoses and their terminal hose connections, as well as sudden drastic failure such as a rupture or leakage due to an overload or the like. More generally, the above mentioned loads and stresses lead to various types of defects in the pressure hoses, from leakage points such as pinpoint holes or ruptures along the length of the hose, to a complete rupture or separation of the hose from its terminal hose connection, for example. The pneumatic or hydraulic fluid (e.g. air or water) leaking out of the hose as a result of such defects causes a reduction of the effectiveness of the associated main weft insertion nozzle and/or auxiliary nozzles connected to the affected hose.
Such a reduction in the operating effectiveness of the fluid nozzles due to defects in the pressure hoses has never yet been monitored or detected in conventional looms up to the present date. The reduction in the operating effectiveness of the weft insertion system necessarily ultimately leads to problems and defects in the weft insertion, which may, however, not be immediately recognized after their occurrence by the operator of the loom. Rather, there is a significant danger that the reduction in weft insertion effectiveness will go unnoticed and uncorrected for an extended period of time during the operation of the loom. As a result, defective weft insertions can be carried out during this period time, and the resulting defectively inserted weft threads will remain as permanent weave defects in the finished woven fabric. This is especially true when the above mentioned defects in the pressure hoses result in only minor leakage at first, but become progressively worse over time, because such a progressive worsening may not be recognized. Thus, the reduction in the weft insertion effectiveness and the corresponding increase in weft defects that is caused by a defective pressure hose in the weft thread insertion system of the loom can lead to the production of a considerable quantity of defective reject fabric, until eventually the operator of the loom notices the defects in the woven fabric and shuts down the loom.